UBC Theses and Dissertations

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UBC Theses and Dissertations

Studies on encapsulation of pelletized biomass Hashemi, Seyedeh Zahra


Hygroscopicity and dust generation are among major challenges to the safe and cost effective use of wood pellets. Wood pellets can rot and disintegrate during storage due to the moisture adsorption from humid environment. In British Columbia, pellets are transported by rail from inland manufacturing plants to a shipping port and stored in silos. At the ports, pellets are loaded from the silo on to the ocean vessel for transport to overseas. Loading is stopped during rain because wood pellets disintegrate when they come into contact with water. The lost revenue from loading shutdown during rain can be large. Furthermore, breakage of wood pellets during handling and storage causes dustiness. Dust and fines may cause adverse health effect, fire, and explosion in storage and silos. Encapsulation of wood pellets with a hydrophobic membrane or surface modification can be a good way to increase water repellent capacity of wood pellets, and avoid dust generation. In this research, commercial wood pellets were coated with a wax solution, linseed oil, cellulose acetate, canola oil, etc. The treated pellets were either dipped in water or exposed to humid environment. The results showed that the investigated liquid coatings increased the durability of wood pellets in water. However, the tested liquid coatings did not decrease water vapor adsorption of pellets significantly. Surface treatments with O₂ etching and CF₄ plasma were applied to render wood pellets hydrophobic. It was demonstrated that CF₄ plasma treatment increased water repellency of wood pellets while O₂ etching without CF₄ deposition step made pellets more hydrophilic. Surface modification with O₂ etching combined with CF₄ deposition created the most hydrophobic surface when pellets were dipped in water. However this combined plasma treatment did not decrease water vapor adsorption from humid environment.

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